Hello Fellows,
The car is a 1986 760 (B230FT). 450k Kms. Everything has been working just lovely for about a year - I was getting the best gas mileage I've ever had with this car - up until this weekend.
This past weekend I was out to a friend's vacation property twice. The trip is about 100 Kms each direction, so about 200Kms round trip, 400Kms total for the weekend. Almost all of it on the highway.
The first two legs of this trip (out and back) on Saturday were fine. No problems whatsoever.
The first leg (out) on Sunday also seemed fine. No irregularities at all.
The trip home however was not so great.
It all came on very slowly, or it seemed to. When I left the cottage everything seemed to be working fine. I've been losing a larger than normal amount of oil for the past month or so, but I didn't think too much of it as I'm pretty sure my distributor seals are gone.
As the trip progressed the car seemed to be down-shifting a lot. I was a little perplexed by this but decided to ignore it until I got home and could take a better look at things. No sense worrying the wife over something small that I can't look into until I'm home anyway...
At first it was just down-shifting on the hills. Eventually it was down-shifting every time I touched the gas pedal. Now I knew something was wrong. I did my best to feather the pedal and get us back home.
When I did get back into town, (where I had to drive slower and there was also some stop-and-speed-up-again situations) I could tell something was really wrong. The car was idling terribly (RPMs seemed about right but it was shaking madly and it felt/sounded like it was going to stall out) and there was a bad oil vapour smell, and it seemed to have no power at all. Actually, if I could get it rolling I could pretty much keep the speed up, (up to about 100Km/h) but it had no acceleration at all.
I finally did get it home but I did not find what I expected to find.
I have had trouble with holes in the turbo intake hoses before, and the symptoms seemed similar to me, so I dutifully checked all those hoses for problems. Actually, I pulled all the turbo ducting out and cleaned it, inspected it, and reinstalled. I even removed the bypass valve and cleaned that. There did not appear to be anything wrong with any of those hoses. They were however COVERED in oil. All the way up to the intercooler. I didn't take any of the ducting on the intake side of the intercooler off but it probably had oil in it too. The outside of everything also seemed to be covered in oil, but those hoses have been like that for ages. I read here that this can mean the bypass valve is shot, but I have had a hard time sourcing one, and it wasn't really causing any problems except for the oil so I just left it.
This time however, it lost a lot of oil. I was down over a litre by the time I got home. I suspect a lot of that has to do with running the turbo so hard, as I tend to lose a bit of oil when I'm really into the turbo anyway - but this was pretty bad to lose over a litre in 100Kms.
When I was playing with it in the driveway, I revved the engine up by turning the throttle spool with my hand. To my surprise the oil dipstick shot out of its tube, with a gush of white smoke behind it. I was lucky it didn't smash me in the face, actually.
Obviously I began to suspect excessive crankcase pressure was a symptom of my problem as well, but I've never heard of it causing power problems before - only the dipstick-popping and resulting oil bath. Also I've never heard the oil vapour described as 'white', which mine definitely was. The car passes the prescribed 'jiggle test' at idle, but the oil filler cap nearly shoots off the valve cover completely with throttle.
I measured the voltage output of the O2 sensor and it seemed to be basically in line with what I expected.
I pinched the fuel line and the car stumbled more - so I can loosely conclude it's getting enough fuel.
I pinched the fuel return line and the car stumbled more - so I can loosely conclude it's not getting too much fuel.
The turbo wasn't/isn't making any noise, and seems to be functioning correctly - I'm not very suspicious of it.
I guess maybe my next step it to do a compression test. ???
Any help about what the problem might be or what I should look into next is a great help, as I am clean out of ideas.
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1986 760 (B230FT) 420k+
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